Sukie (oz14654)

About this Plan

Sukie. Radio control sport model, for 40 power.

Quote: "Free Plan. A lively 56 in span mid-wing 40 sized sports aerobatic model for 4 functions. Sukie, by John Hancock.

Here we go again, yet another sport 40 club aerobatic Sunday morning whizzer. We all build them because they are great fun to fly, fit in the car in one piece and keep the hands and eyes in gear, they are part of the staple aeromodelling diet.

This one has evolved through several models rather than bursting upon the scene as a masterstroke of contemporary thought. When I first flew it I thought that it seemed a good individual aeroplane, so I made another one and I was pleased to find that it flew identically. I still have both of them and have discovered no Achilles heels. The model has a certain nimble quality that is very appealing.

As far as formal design goes, the CG/neutral point position checks out nicely against Alasdair Sutherland's recent nomograms - thank you for the wise words sir. My method of estimating CG/neutral point goes back to the fifties but surprisingly correlates well with current thought. It is reassuring to have everything brought up to date.

One further thought about design. We all know that 'what looks right flies right', but how do you get to know what looks right? Now that was a rhetorical question because in truth much model aeroplane design is necessarily based on observation and experience rather than calculation. By that I mean that the detail and outlines of a good model are usually honed to an edge by informed development rather than calculation. So many of our calculated elements are dependent somewhere on empirical factors anyway - which comes back to somebody elses observation and experience. So is it art, craft or engineering? I think Wilbur Wright was a classical example of this approach, he would have made a really great aeromodeller. Now, about this aeroplane.

Construction: Notes rather than blow by blow for this section because this is unlikely to be your first scratch built model.

Wings: The drawing shows a built up structure which is the one employed on my first model. The wing is built upside down on a flat building board so that the taper generates slight dihedral on the underside. No washout is employed, or necessary. Make a belt, braces and hairy string job of the dowel fixing at the leading edge, the aeroplane hangs on it and all the 'g' forces go through it.

My second model employs a foam wing commissioned from Humberside Models. No problems and certainly no criticisms, but the penalty is 7 oz more weight than the built up wing. The cost of the two constructions is very similar.

As a general comment on wing finishing I always seal my structures and cover with tissue, followed by a light coat of dope to finish off. This stiffens an open structure and if lightly rubbed down, gives a better base for a heat shrink film. If wallpaper paste is used as the tissue adhered, a repair is simplified because both film and base tissue can be very easily peeled from large sheet areas. This particular built up wing structure is quite adequately stiff in torsion and so the builder has a choice and could save a little weight over my original model.

Building the Fuselage: This is a totally conventional slabside box structure. Pin down a thread centre line on the building board and always mark the centre line on each former. Choose the side sheets carefully so that they have matching stiffness..."

Sukie from R/C Model World, April 2001.

Direct submission to Outerzone.

Supplementary file notes

Article pages, thanks to RFJ.

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